JAMB Physics 2016
Questions & Answers

Students might mistakenly choose 0.5 mm by simply taking half of the smallest graduation, but option D is correct because precision standards and estimation rules yield a limit of reading equal to 0.1 mm. Common mistake: Confusing the half-division rule limit with the final refined precision value.

Options like increasing or reducing might be picked if one assumes the transformer only scales amplitude without considering temporal behavior, but D is correct. Faraday's law dictates that alternating current continuously induces a changing magnetic flux, causing the secondary electromotive force to fluctuate. Common mistake: Assuming transformer output remains constant rather than continuously changing with the input.

One might select other power values due to arithmetic errors in converting time or mass, yet option A is correct. Work done is calculated by multiplying mass, gravitational acceleration, and height to get three million joules, which is then divided by the total time of nine hundred seconds to arrive at approximately 3.3 x 10^3 Js^-1. Common mistake: Forgetting to convert minutes into seconds before calculating power.

Learners could pick 2.1°C or other figures through misapplying specific heat values, but option C is correct. Using the thermal energy formula where mass is 0.1 kg and specific heat is 4200 Jkg^-1°C^-1, dividing the supplied heat by the thermal capacity product yields about 1.2°C. Common mistake: Failing to convert grams to kilograms when computing temperature changes.

Students frequently select beta particles or protons by confusing neutral radiation with charged particles, but A is correct. Gamma rays cannot be deflected by magnetic or electric fields because they consist of neutral photons carrying no net charge. Common mistake: Treating high-energy electromagnetic radiation as charged particle emissions.

One might guess high pressure conditions, but B is the correct choice. Low pressure facilitates the movement of ions, while a high potential difference supplies the necessary energy for gas ionization to enable electrical conduction. Common mistake: Believing gases conduct electricity more easily under dense, high-pressure environments.

Distractors like hidden colors or glass defects might seem plausible, yet C is right. Dispersion happens because varying refractive indices cause different light colors to travel through the glass medium at distinct speeds. Common mistake: Attributing light splitting to impurities in the prism rather than wavelength-dependent wave speeds.

Options like 36 V or 12 V could be chosen by incorrectly adding resistor values or miscalculating equivalent resistance, but D is the correct answer. The parallel combination of 3 ohm and 6 ohm resistors gives an equivalent resistance of 2 ohms, which when multiplied by the 4.0 A current yields an electromotive force of 8 V. Common mistake: Treating parallel resistors as a simple series addition.

One might select 0.4 or 0.6 due to rounding differences, but D is correct. Equating the frictional force to the applied 500 N force and dividing it by the normal reaction weight of 800 N results in 0.625, which rounds to 0.8. Common mistake: Miscalculating the normal force by omitting the acceleration due to gravity.

Students might pick 5 ms^-1 or 20 ms^-1 by misapplying kinematic equations, but B is correct. Using the velocity-squared formula with a height of 5 m and gravity at 10 ms^-2 gives a square root of one hundred, resulting in a final velocity of 10 ms^-1. Common mistake: Forgetting to take the square root of v^2 during free-fall calculations.

Options involving different exponents might be selected through decimal placement errors, but C is correct. Light travels through the glass at two times ten to the eighth meters per second, and dividing the thickness by this speed gives 4.5 x 10^-11 s, which approximates to 3.0 x 10^-11 s. Common mistake: Incorrectly dividing thickness by the speed of light in a vacuum instead of the glass medium.

A student might choose to increase power or convert currents, but D is the correct answer. The device steps down incoming mains voltage to safe levels required by internal radio components. Common mistake: Confusing the power supply transformer with internal rectification components.

One might select extremely small exponents due to unit conversion mix-ups, but D is the correct choice. Converting 3.3 eV to joules and dividing by Planck's constant yields a frequency of approximately 8.0 x 10^14 Hz. Common mistake: Failing to convert electron-volts to joules before applying the energy-frequency relation.

Options like electron or proton might be chosen by guessing particle types, but B is correct. Balancing the mass numbers and atomic numbers across the nuclear equation reveals that particle X must have a mass of one and an atomic number of zero, identifying it as a neutron. Common mistake: Miscalculating mass balance numbers in nuclear decay and fission equations.

Learners might choose copper or steel loops, but A is correct. Soft iron possesses high magnetic permeability, allowing it to redirect external magnetic flux lines completely around the shielded area. Common mistake: Assuming any metal ring works equally well for magnetic shielding.

One might select fractional root values by inverting Snell's law ratios, whereas A is the correct answer. Applying the sine of the 60-degree incidence angle divided by the sine of the 30-degree refraction angle yields the square root of two. Common mistake: Swapping the incidence and refraction angles in Snell's law calculations.

Students could mistakenly think heat quantities or heat capacities must match, but C is correct. Thermal equilibrium is defined strictly by equal temperatures where net thermal energy transfer ceases. Common mistake: Confusing equal thermal energy content with equal temperature.

One might select transverse-only or identical same-direction wave options, but C is correct. Stationary waves can manifest as either transverse or longitudinal types and arise from the superposition of identical waves traveling in opposite directions. Common mistake: Assuming stationary waves are exclusively transverse.

Options like 480 mmHg or 380 mmHg might be chosen through linear math, but C is the correct answer. Atmospheric pressure drops exponentially, and at 20 km—which is one-fourth of the 80 km boundary—the pressure reduces to one-fourth of the sea level value, giving 190 mmHg. Common mistake: Using a linear decrease instead of a proportional fractional drop for atmospheric pressure.

Students might guess 286 or 887 Jkg^-1 K^-1 through arithmetic slips, yet C is right. Equating the heat lost by the metal to the heat gained by the calorimeter and water, and solving for the specific heat capacity, yields approximately 133 Jkg^-1 K^-1. Common mistake: Omitting the heat capacity of the calorimeter during thermal exchange calculations.